1. Field of the Invention
The present invention relates to a focus position control apparatus and a camera.
This application claims priority to and the benefit of Japanese Patent Application No. 2009-075727 filed on Mar. 26, 2009, the disclosure of which is incorporated herein by reference.
2. Background Art
An exemplary conventional focus position control apparatus for performing autofocus in a digital camera, a video camera, and so on. controls a focus position using, for example, a scheme called a hill climbing control scheme or a through the lens (TTL) phase difference scheme in detecting a focus state of an imaging lens.
The hill climbing control scheme involves acquiring an image signal from an imaging element while moving an imaging lens in a direction along an optical axis, searching for a maximum peak value in a change of a focusing evaluation value of the image signal, and determining an imaging lens position, at which the maximum peak value is obtained, as a focusing position. For example, a contrast value in a focus area may be used as the focusing evaluation value.
The TTL phase difference scheme involves evaluating a focus state of an imaging lens and searching for a focusing position by dividing a pupil of an imaging lens into a pair of regions and detecting a relative change of positions of a pair of images formed by light flux passing through the divided pupil regions.
For example, in Japanese Patent Laid-open Publication No. 2007-121580, an autofocus apparatus for controlling a focus position using a hill climbing control scheme of calculating evaluation value data based on an image signal input to a sensor circuit via a lens while moving the lens step by step, and specifying the focusing position from a size of the evaluation value data is described.
In Japanese Patent Laid-open Publication No. 2007-121580, an origin position of a lens is detected when power is turned on, the lens is moved to a specific position at a very proximal side, and the lens is gradually moved from the specific position at the very proximal side to a distal side, for autofocus using a hill climbing scheme.